Round balers have become quite prevalent for their capability of producing a conveniently sized cylindrical bale, very often automatically wrapped with a sheeting material such as net or film. Crop material, such as hay, is picked up from the ground as the baler travels across the field, and is fed into an expandable chamber where it is rolled up to form a compact cylindrical hay package.
Prior art round balers generally have an expandable bale chamber defined by a pair of fixed sidewalls, and a plurality of side-by-side belts cooperating with a series of transverse rolls, mounted between a pair of pivotally mounted arms commonly known as a sledge. The chamber includes an inlet opening in the front through which crop material is fed. Also included is a pair of take up arms pivotally mounted on the main frame, between which arms multiple of guide rolls are journalled. A biasing force is applied on the take up arms to urge the outer surfaces of the guide rolls against the belts to maintain belt tension and prevent slack from occurring in the belts during expansion and contraction of the chamber.
It is known to provide a round baler density system to apply increased tension on the belts in order to create a densely packed bale. A hydraulic density cylinder with a controlled fluid release limits the rate of bale chamber expansion and provides a degree of crop compaction during baling. The amount of compaction may be varied by adjusting the fluid release rate, often in the form of a pressure relief valve which restricts the extension of the density cylinder by forcing fluid through a variable relief. When the bale reaches a desired size and is discharged, mechanical springs acting on the take up arms are typically employed to return the hydraulic cylinder to its initial position and provide a biasing force on the take up arms so a new bale forming cycle may commence.
Problems arise when the baler is used on silage crops which typically have higher moisture content and are suppler. The additional moisture reduces the friction coefficient between the belts and the drive roll. The supple crop has a tendency to build up on the rollers and scrapers in the baler, increasing friction and requiring more power to turn the belts. The combination increases incidence of belt slipping, making the task of commencing the bale-forming cycle by rolling the then-stationary belts all the more difficult.
It would be desirable to provide a system that would increase the tension in the belts to improve belt rolling during the initial phase of bale formation. Additional advantages would be realized by a system that would selectively increase belt tension during the bale initial phase yet allow use of the current bale density systems once the bale forming process is under way. Still further advantages would be realized through an improved belt tensioning system that could be easily implemented on existing bale tensioning systems without requiring a dramatic changes to the bale tensioning system.